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CD4分子是单链跨膜糖蛋白,分子量55Kd,由四个胞外功能区(E1～E4)、跨膜区和胞浆区组成.胞外功能区E_1与Ig_k链v区有同源性,胞浆区尾部与P56~(LCK)相连.CD4可与MHCⅡ类分子的非多形性部分结合.CD4与MHCⅡ类分子结合位点广泛地分布在E_1,E_2和E_3的N端.这两种分子结合可增强CD4~+T细胞与抗原呈递细胞之间的粘附性,提高CD4~+T细胞识别抗原的敏感性,并通过CD4-P56~(LCK)传递信号促进T细胞活化,此外,CD4分子对未成熟T细胞在胸腺内分化成熟过程有重要作用.
The CD4 molecule is a single-stranded transmembrane glycoprotein with a molecular weight of 55Kd and consists of four extracellular domains (E1-E4), transmembrane and cytoplasmic domains, and the extracellular domain E_1 has homology with the Ig_k chain v- The cytoplasmic tail is linked to P56 ~ (LCK), and CD4 binds to the non-polymorphic part of MHC class II molecules.The binding sites of CD4 and MHC class II molecules are widely distributed at the N-terminus of E_1, E_2 and E_3 Molecule binding enhances the adhesion between CD4 ~ + T cells and antigen-presenting cells, enhances the sensitivity of CD4 ~ + T cells to recognize antigens, and promotes the activation of T cells through CD4 ~ P56 ~ (LCK) signaling. In addition, CD4 molecules immature T cells in the thymus differentiation and maturation process has an important role.